Vocal nodules are calluses that form on the lips of the vocal folds because of persistent contact abuse. The nodules disrupt the movement and vibration of the vocal folds during singing (and speaking). The deeper cause of vocal nodules is weak and uncoordinated muscular action in the larynx (and a constricted pharynx), which prevents the vocal musculature from managing efficiently the stresses of voice production.
For singers, the inability to observe directly the actual functioning of their vocal apparatus, and the lack of sensations during singing, have caused not a little mischief, not the least of which is that singers often do significant damage to their vocal apparatus without being aware of it. Some students with vocal nodules will make statements like, "I feel fine, but my high notes were there last week, and now they're gone; I don't know what happened or what to do to get them back." It is very common for a singer, for example, to begin experiencing difficulties with hoarseness, loss of vocal power, and range only to discover upon a medical examination that he has developed vocal nodules. Vocal nodules develop over time as a result of habitual, abrasive vocal fold contact. Yet, singers are always taken aback to discover that, despite the physical abuse that they have perpetrated on their own vocal folds, they typically didn’t feel pain or physical discomfort as the nodules were being formed. Although vocal nodules often produce no physical sensations, under certain conditions, singing could be physically uncomfortable. In some cases, the muscular constriction could become so advanced that a singer feels strangling-like sensations in the throat during singing—especially when he is struggling to produce high notes. With the extreme participation of extraneous muscles, singing could even become physically exhausting.
The breakdown of any part of the voice’s muscular system creates other imbalances and results in an overall loss of muscular strength and coordination action between all the actions of phonation. This situation typically leads to the engagement of extraneous muscles during singing. Muscles of the neck and chest, for example, could come into play to try to compensate for the failure of the larynx, pharynx, and soft palate to carry out their workload in a balanced and efficient way. Unfortunately, these fallback maneuvers don't work and contribute to the further weakening of laryngeal, pharyngeal, and soft palate musculature.
Furthermore, training the soft palate to remain low (relaxed) during singing also has the effect of causing the larynx to rise in the throat; over time this upward movement will become an uncontrollable spasmodic upward thrust that will weaken muscular actions of the vocal folds and those that control the movement of the larynx as a whole. In this scenario, the overall loss of coordination and muscular support in the larynx and pharynx is unavoidable. A variety of speaking and singing disorders could develop from this condition such as hoarseness, loss of vowel resonance, vocal weakness, range reduction, vocal nodules, and general vocal deterioration.
Additionally, Singing in keys too high for one’s voice—in the wrong "tessitura" (comfortable range)—for instance, causes the larynx to rise in an unhealthy, stressful fashion, which often leads to vocal deterioration and vocal disorders like vocal nodules (calluses). Please take special note that it is very dangerous to exercise the falsetto voice directly (and to sing a great deal in the falsetto voice) as it could lead to voice disorders like vocal nodules.
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